The invention relates to the use of a splicing tape to equip a wound roll for flying splice, to a splicing method, and to the splicing tapes used in said method.
Flat materials in web form, more particularly paper, are wound into rolls. Such rolls are supplied, for example, to paper-processing machines or to printing and/or packaging machines. In the ongoing operation of such installations it is necessary to locate and appropriately join the start of a new wound roll, in a changeover on the fly, to the end of a first roll of the flat material in web form, without having to halt the high-speed machines when changing the rolls over. This operation is referred to as splicing.
Within the paper industry it is performed using double-sided self-adhesive tapes which consist essentially of a carrier layer and two layers of self-adhesive, to produce a join between the end of the old material web and the start of the new material web. The end of the old material web is bonded in the process to the start of the new material web.
Likewise known are adhesive tapes having a splittable system, comprising a material which separates between top and bottom face when subjected to normal force. EP 1 076 026 A2 describes a splicing tape with fixing aid, the fixing aid consisting of a carrier material which is formed from two co-laminated planar materials, the lamination forming a predetermined breakage point, and the fixing aid being given pressure-sensitive adhesion qualities on its bottom face. EP 1 640 301 A1 likewise describes an adhesive tape for producing a join in flying splice, with a splittable system, the splittable system being composed of two layers which can be separated from one another. An adhesive tape for producing a splice join is described, furthermore, in EP 1 630 116 A2. This adhesive tape comprises a carrier material, which is coated on its top face with a self-adhesive composition and provided on the opposite face with a splittable system, the splittable system opening along a parting plane between two layers. Another splicing tape is described in EP 1 318 962 B1, that tape comprising two substrates joined separably to one another via a layer of adhesive.
The systems described to date are restricted, in some cases very much so, in their applicability. For example, in the case of automated processes, in which the splicing tapes are applied to a wound roll, with the splicing tapes described to date there are often instances of damage in the region of the predetermined breakage point. Furthermore, in the systems specified above, the difficulty exists of setting the splitting system in such a way that on the one hand the risk of unwanted initial splitting in the acceleration phase is avoided, while on the other hand the proper splitting of the splicing tape, without damage to the webs of material to be joined, is ensured. One approach to a solution involves specifically setting the parting forces of a full-area splitting system. In a splitting system configured on a full-area basis, however, the splitting system must always represent a compromise. The reason for this is that, in order to overcome the splitting resistance at the leading edge, an increased, maximum force is required for initial splitting of the system (initial splitting force). Furthermore, a force at a lower level is needed for splitting over the entire width of the splicing tape (split propagation force). The product of the force times the width of the splitting system is the energy needed for splitting (splitting energy). In a full-area system, on the one hand, the initial splitting force must be set high enough that the product does not open prematurely, as a result of the aerodynamic forces and centrifugal forces that act during acceleration, while on the other hand the splitting energy set must be low enough that the required energy for the complete and comprehensive splitting of the splitting system does not result in instances of tearing. With full-area splitting systems in particular, this compromise is difficult to establish. This problem is manifested especially with thin and therefore sensitive systems.